1. Please buy a box of corn starch (Any brand will do. )
2. In a large bowl mix a cup of the corn starch with an approximately half the amount of water. Kneed the mixture with your hands. Add more water slowly.
3. Adjust the mixture by adding more starch or more water.
When you have a good mixture, the glop will act like a solid when you put pressure on it. You can crack it and crumble it like a solid. When the pressure is released, the glop acts like a liquid flowing through your hand.
A polymer is a long chain of repeating sub-units. Starch is a polymer of sugar molecules, a complex carbohydrate.
The sugars in the starch have OH bonds which can interact and stick together by something called hydrogen bonding. Hydrogen bonding is not nearly as strong as the covalent bonds but in this case they are strong enough to make the glop act like a solid. Because there are OH bonds in water too, if the glop is allowed to flow at its own pace, the water and starch will form new hydrogen bonds as the old ones break. When it does so, the glop can change shape and flow like a liquid.
Tricks to success: You have to have the right mixture. If you have too much water then the above process can occur rapidly and the mixture acts like a liquid all the time. If there is too little water then the hydrogen-bond breaking bond reforming process occurs too slowly and the glop just sits there like a solid. Have fun and keep playing! Remember, it is just starch. It will vacuum out of carpet and is pretty non-toxic.
In the discussion section please comment on your experiment in one of three areas:
1) Describe your observations and thoughts on this exercise. (It reminded me of terminator II)
2) Hydrogen bonding plays a key role in the structure of water, DNA and proteins. If you can find a good site on hydrogen bonding, share the address with us and tell us what you like about it. I like http://www.mrs.umn.edu/~goochv/CellBio/lectures/water/water.html because the first 2 paragraphs are well written and the pictures are good.
3) Are there other web sites that describe polymer experiments that you can do at home? (yes) If you try out another recipe, please tell us how it worked.
Please put your response in the discussion category marked "polymer"